This invention relates to a process for the purification of higher olefins by removal therefrom of phosphine impurities, particularly phosphine impurities representing residues of catalysts utilized in preparation of the olefins.
It is known in the art to prepare higher olefins (i.e., those having a carbon number of at least six) by the oligomerization of lower olefins, most commonly ethylene, over a catalyst which comprises a phosphine component. Such oligomerization processes are described, for instance, in U.S. Pat. No. 4,528,416 and other patents cited therein.
Higher olefins find their principal utility as intermediates in the preparation of a very wide variety of end products. For example, olefin products having carbon numbers predominantly in the C.sub.6 to C.sub.20 range are known to be particularly useful as intermediates in the preparation of surfactants, lubricants, polymers and plasticizers. In the practice of various processes for synthesizing such end products from higher olefins, it has on occasion been observed that small amounts of residual phosphine impurities substantially interfere with the processing of the olefin or adversely influence the properties of the end product. Accordingly, a process for the effective removal of phosphine impurities from higher olefins would be highly desirable.
The present invention most particularly relates to a process for the removal of phosphine impurities from an olefin containing such impurities, which comprises a step for the contact of the olefin with a cation exchange resin in the acid, or hydrogen ion, form. In this respect, the prior art is found to disclose that an anion exchange resin can be used to eliminate phosphate values from water. U.S. Pat. No. 3,579,322 specifically describes contacting a waste aqueous stream containing phosphate values with a cation exchange resin bed to remove cations followed by contact of the cation-free stream with an anion exchange resin to eliminate the phosphate values. In an alternative process, this patent teaches contact of the aqueous stream directly with a weak-base anion exchange resin for removal of phosphate values. The published Japanese patent application No. 5 5-8017-885 describes contact of water containing both phosphate and a magnesium salt with an ion exchange resin in the calcium form. This contact yields an ion exchange in the magnesium form, and calcium phosphate which can be precipitated from aqueous solution. The published Japanese application No. 5-3031-572 discloses a process for removal of phosphoric acid ions from aqueous solution using an ion exchange means exemplified by Al.sub.2 O.sub.3, La.sub.2 O.sub.3, and Group VIII metal oxides.